Significant genetic differentiation among populations of Anomalocardia brasiliana (Gmelin, 1791): A bivalve with planktonic larval dispersion

Four Brazilian populations of Anomalocardia brasiliana were tested for mutual genetic homogeneity, using data from 123 sequences of the mtDNA cytochrome oxidase c subunit I gene. A total of 36 haplotypes were identified, those shared being H3 (Canela Island, Prainha and Acupe) and both H5 and H9 (Prainha and Acupe). Haplotype diversity values were high, except for the Camurupim population, whereas nucleotide values were low in all the populations, except for that of Acupe. Only the Prainha population showed a deviation from neutrality and the SSD test did not reject the demographic expansion hypothesis. Fst values showed that the Prainha and Acupe populations represent a single stock, whereas in both the Canela Island and Camurupim stocks, population structures are different and independent. The observed structure at Canela Island may be due to the geographic distance between this population and the remainder. The Camurupim population does not share any haplotype with the remaining populations in northeastern Brazil. The apparent isolation could be due to the rocky barrier located facing the mouth of the Mamanguape River. The results highlight the importance of wide-scale studies to identify and conserve local genetic diversity, especially where migration is restricted

Long telomeres are associated with clonality in wild populations of the fissiparous starfish Coscinasterias tenuispina

7 páginas, 4 figuras, 3 tablasTelomeres usually shorten during an organism’s lifespan and have thus been used as an aging and health marker. When telomeres become sufficiently short, senescence is induced. The most common method of restoring telomere length is via telomerase reverse transcriptase activity, highly expressed during embryogenesis. However, although asexual reproduction from adult tissues has an important role in the life cycles of certain species, its effect on the aging and fitness of wild populations, as well as its implications for the long-term survival of populations with limited genetic variation, is largely unknown. Here we compare relative telomere length of 58 individuals from four populations of the asexually reproducing starfish Coscinasterias tenuispina. Additionally, 12 individuals were used to compare telomere lengths in regenerating and non-regenerating arms, in two different tissues (tube feet and pyloric cecum). The level of clonality was assessed by genotyping the populations based on 12 specific microsatellite loci and relative telomere length was measured via quantitative PCR. The results revealed significantly longer telomeres in Mediterranean populations than Atlantic ones as demonstrated by the Kruskal–Wallis test (K=24.17, significant value: P-valueo0.001), with the former also characterized by higher levels of clonality derived from asexual reproduction. Telomeres were furthermore significantly longer in regenerating arms than in non-regenerating arms within individuals (pyloric cecum tissue: Mann–Whitney test, V=299, P-valueo10− 6; and tube feet tissue Student's t= 2.28, P-value =0.029). Our study suggests that one of the mechanisms responsible for the long-term somatic maintenance and persistence of clonal populations is telomere elongation.This research was financially supported by a PhD fellowship FPI-MICINN (BES-2011-044154) (ACG), the European ASSEMBLY project (227799), the Swedish Royal Academy of Sciences (ACG) and the Spanish Government project CTM2010-22218-C02. The research was also supported by a ‘Juan de la Cierva’ contract from the Spanish Government (RPP) and by the Adlerbertska Research Foundation (HNS).Peer reviewe

Reproductive cycle of the endemic cassiduloid Cassidulus mitis (Echinoidea : Cassiduloida) on the Brazilian coast

Cassidulus mitis Krau, 1954 is an endemic species from Rio de Janeiro, Brazil. To study the reproductive cycle of this species, samples were collected at Praia Vermelha, in Guanabara Bay, from Octo er 1998 to April 2000. The sex ratio for C. mitis was 1: 1, and reproduction occurred throughout the year. The gonadal index of males was greater than that of females. Five gametogenic stages were identified in males: early growth, premature, mature, partially spawned and early growth with a partially spawned stage. There were no spent or recovery stages such as those seen in females. Females had six gametogenic stages: recovery, early growth, premature, mature, partially spawned and spent stage; there was no early growth with a partially spawned stage as there was in males. The mean oocyte diameter was 382 mum (SD=49 mum), and the mean number of juveniles per female was 100 individuals (SD=108). The anterior gonads were frequently smaller than the posterior ones, and there were differences in the gametogenic stages between the anterior and posterior gonads. First sexual maturation occurred in individuals with a diameter of 17 mm. The intestinal wet weight was two- to threefold higher than the test wet weight. This may indicate that C. mitis uses its intestine as a "weight belt" to avoid displacement from the substratum.145360361

Experimental evaluation of rhodoliths as living substrata for infauna at the Abrolhos Bank, Brazil

Over large areas of the Brazilian continental shelf, coralline algal rhodoliths provide habitats with high community diversity. In order to understand the role of rhodoliths in structuring the poorly studied infauna of these habitats, we determined seasonal patterns of their size and shape related to the associated biota, and experimentally tested the influence of living substrata in the Abrolhos Archipelago marine protected area. Samples (n = 20) were randomly collected from a rhodolith bed using cores (~1.7 L) during three seasons of the year. Subsamples were sorted by grain size, dry weight, degree of thallus branching, and associated invertebrate taxa. Live and dead rhodoliths with invertebrates removed and control samples with invertebrates present (n = 6) were transplanted inside baskets into the bed to test substrate associations. Transplanted samples were compared with natural ones directly collected from the rhodolith bed after nearly three months. The most common rhodolith-forming species was Mesophyllum erubescens. Polychaetes were usually the dominant taxon, making up 63% of the total infauna. The most common infaunal species was the polychaete Exogone dispar. There was a general seasonal trend of a reduction in invertebrate abundance from autumn/winter to spring. Amphipods were dominant in autumn (70% of sample) but half as abundant in winter and spring when their population density was similar to that of polychaetes (49%). Ophiuroids and molluscs were less abundant (up to 1% and 5% of the total sample). Polychaete abundance was significantly lower in live than in dead transplanted rhodoliths, whereas amphipods showed no difference. Variation in infaunal abundances was related to variability in habitat heterogeneity due to changes in rhodolith size and shape resulting from changes in water turbulence. The calcareous thalli of rhodoliths not only build complex calcareous gravels but also affect community diversity providing a refuge for infaunal groups.

Reproductive biology of Echinometra lucunter (Echinodermata: Echinoidea) in a northeast Brazilian sandstone reef

The edible sea urchin Echinometra lucunter (Linnaeus, 1758) is a very common species on the sublittoral-midlittoral in Brazilian rocky shores. The aim of this work was to describe the gametogenesis and reproductive strategy of the E. lucunter population at Muro Alto beach in the Northeast coast of Brazil from August 2004 to August 2005. A total of 240 specimens were collected on the sandstone reef flat from a tidepool during spring low tides. The overall sex ratio was1.12:1,withoutsignificanttemporalvariationexceptinOctober2004. Firsts sexual maturity ocurred in individuals from a diameter of 20.8 mm. There was not a significant difference in gonad index between females and males during the sampling period. The female's gonad index variation was associated with a well-defined spawning, corroborated by the histological analysis of the gonads, which demonstrates sex differences of the gamete production. By contrast, the males showed no clear pattern. It is suggested that continuous reproduction with seasonal peaks in the E. lucunter population occurs at Muro Alto beach.<br>O ouriço-do-mar comestível Echinometra lucunter (Linnaeus, 1758) é uma espécie muito comum no infralitoral e mediolitoral do Brasil. O objetivo deste trabalho foi descrever a gametogênese e a estratégia reprodutiva da população de E. lucunterna praia de Muro Alto entre agosto de 2004 e agosto de 2005. Um total de 240 espécimes foi capturado de uma poça de maré situada no topo recifal, durante as marés baixas de sizígia. A razão sexual total foi de 1,12:1 sem variação temporal significativa, exceto em outubro de 2004. A primeira maturidade sexual ocorreu em indivíduos a partir de 20,8 mm de diâmetro. Não houve nenhuma diferença significativa no índice gonadal entre fêmeas e machos durante o período de amostragem. A variação do índice gonadal das fêmeas foi associada a um período de desova bem definido, corroborado pela análise histológica das gônadas, que demonstra diferenças sexuais na produção de gametas. Ao contrário, os machos não apresentaram nenhum padrão. Sugere-se que a reprodução da população de E. lucunter na praia de Muro Alto é contínua, compicos sazonais